WO2019106795A1

WO2019106795A1 - Refrigeration cycle device

Info

Publication number: WO2019106795A1
Application number: PCT/JP2017/043118
Authority: WO
Inventors: 宗希石山
Original assignee: 三菱電機株式会社
Priority date: 2017-11-30
Filing date: 2017-11-30
Publication date: 2019-06-06
Also published as: CN111386434A; US11635234B2; US20200309435A1; JPWO2019106795A1; JP7107964B2; EP3719413A1; EP3719413A4

Abstract

According to the present invention, a control device (10) switches an operation mode of a refrigeration cycle device (100) between a heating operation mode and an oil recovery operation mode upon receiving a command for a heating operation. The heating operation mode is a mode for circulating a refrigerant inside a refrigerant circuit (20) so that the refrigerant in a gaseous phase state flows through a gas extension pipe (15). The oil recovery operation mode is a mode for circulating the refrigerant inside the refrigerant circuit (20) so that the refrigerant in a gas-liquid two-phase state flows through the gas extension pipe (15). The direction of the flow of the refrigerant inside the gas extension pipe (15) in the oil recovery operation mode is opposite to the direction of the flow of the refrigerant inside the gas extension pipe (15) in the heating operation mode.

Description

Refrigeration cycle device

The present disclosure relates to a refrigeration cycle apparatus, and more particularly to a refrigeration cycle apparatus that recovers refrigeration oil in a refrigerant circuit to a compressor.

BACKGROUND Conventionally, a refrigeration cycle apparatus is known that includes a refrigerant circuit in which a compressor, a first heat exchanger, a pressure reducing device, and a second heat exchanger are connected by a refrigerant pipe. In such a refrigeration cycle apparatus, refrigeration oil may be discharged from the compressor together with the refrigerant, and refrigeration oil may stay in the refrigerant circuit. When the refrigeration oil stagnates in the refrigerant circuit, the amount of refrigeration oil in the compressor decreases, a load is applied to the shaft in the compressor, and the compressor is likely to break down.

Japanese Patent Laid-Open No. 2008-180421 (Patent Document 1) discloses a technique for increasing the operating frequency of a compressor in order to recover refrigeration oil accumulated in a refrigerant circuit to the compressor.

JP 2008-180421 A

In recent years, with the increase of high insulation and high airtightness buildings, the frequency of intermittent operation of the refrigeration cycle apparatus is high. In the intermittent operation, the difference between the temperature of the room to be air-conditioned and the target temperature is small, and the compressor is operated intermittently. FIG. 13 is a diagram showing time changes of the frequency of the compressor, the room temperature, and the amount of refrigerating machine oil in the compressor in the prior art. The time change at the time of heating operation is shown by FIG. As shown in FIG. 13, refrigeration oil is discharged from the inside of the compressor into the refrigerant circuit when the compressor is started. However, since the compressor operates at a low frequency, refrigeration oil stagnates in the refrigerant pipe and is hardly returned to the compressor. In particular, refrigerator oil in the refrigerant in the gas phase has a high viscosity and is difficult to move only by the flow of the refrigerant in the gas phase. Therefore, when the refrigeration cycle apparatus is operated intermittently, the amount of refrigeration oil in the compressor gradually decreases each time the compressor is activated, and an oil depletion state occurs in which the amount of refrigeration oil in the compressor falls below the lower limit value. In the prior art described in Japanese Patent Application Laid-Open No. 2008-180421, when the integrated value of the operating time reaches a specified time, an oil recovery operation is performed to increase the operating frequency of the compressor.

However, since the operating frequency of the compressor is increased in a state where the amount of refrigeration oil is small, a load is applied to the compressor, and a compressor failure such as shaft galling tends to occur.

An object of the present disclosure is to provide a refrigeration cycle apparatus capable of recovering refrigeration oil to a compressor while suppressing occurrence of a failure of the compressor.

The refrigeration cycle apparatus of the present disclosure includes a refrigerant circuit and a controller. In the refrigerant circuit, the compressor, the first heat exchanger, the pressure reducing device, and the second heat exchanger are connected by a refrigerant pipe. The control device switches the operation mode of the refrigeration cycle device between the first operation mode and the second operation mode. The refrigerant pipe includes a first pipe connected to one port of the first heat exchanger. The first operation mode is a mode in which the refrigerant is circulated in the refrigerant circuit so that the refrigerant in the gas phase flows into the first pipe. The second operation mode is a mode in which the refrigerant is circulated in the refrigerant circuit such that the refrigerant in the liquid phase state or the gas-liquid two-phase state flows to the first pipe. The first pipe constitutes a flow passage between the compressor and the first heat exchanger in the first operation mode. The flow direction of the refrigerant in the first pipe in the second operation mode is opposite to the flow direction of the refrigerant in the first pipe in the first operation mode.

According to the present disclosure, refrigeration oil can be recovered to the compressor while suppressing the occurrence of a failure of the compressor.

1 is a schematic configuration diagram of a refrigeration cycle apparatus according to Embodiment 1. FIG. FIG. 7 is a diagram showing the flow direction of the refrigerant in the oil recovery operation mode in the first embodiment. 5 is a flowchart showing a flow of processing of the control device 10 according to the first embodiment. FIG. 7 is a schematic configuration diagram of a refrigeration cycle apparatus according to Embodiment 2. It is a figure which shows the flow of a refrigerant | coolant when it switches from the heating operation mode to the oil collection | recovery operation mode. FIG. 17 is a diagram showing the flow of the refrigerant in the cooling operation mode in the second embodiment. It is a figure which shows the flow of a refrigerant | coolant when it switches from a cooling operation mode to an oil collection | recovery operation mode. 7 is a flowchart showing a flow of processing of a control device according to Embodiment 2; It is a figure which shows the mode of the refrigerator oil in piping when the flow velocity of the refrigerant | coolant of a gaseous-phase state is more than oil rising limit speed. It is a figure which shows the mode of the refrigerator oil in gas extension piping which concerns on the modification 1. FIG. It is a figure which shows the mode of refrigerator oil in gas extension piping which concerns on the modification 2. FIG. It is a figure which shows the flow of the refrigerant | coolant before and behind the switching from heating operation to air conditioning operation. It is a figure in the prior art which shows the time change of the frequency of a compressor, room temperature, and the amount of refrigeration oil in a compressor.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Although a plurality of embodiments will be described below, it is planned from the beginning of the application to appropriately combine the configurations described in the respective embodiments. In the drawings, the same or corresponding portions are denoted by the same reference characters and description thereof will not be repeated. Furthermore, the form of the component shown in the specification full text is an illustration to the last, and is not limited to these descriptions.

Embodiment 1
(Configuration of refrigeration cycle device)
FIG. 1 is a schematic configuration diagram of a refrigeration cycle apparatus according to a first embodiment. Referring to FIG. 1, a refrigeration cycle apparatus 100 includes a refrigerant circuit 20 in which a compressor 1, a four-way valve 2, a first heat exchanger 3, a pressure reducing device 4 and a second heat exchanger 5 are connected by refrigerant piping. The refrigerant is circulated in the refrigerant circuit 20. The first heat exchanger 3 is installed in a room to be air conditioned. The compressor 1, the four-way valve 2, the pressure reducing device 4 and the second heat exchanger 5 are integrated as an outdoor unit and installed outdoors. The refrigerant pipe includes a gas pipe 11, a liquid pipe 12, a refrigerant suction pipe 13, a refrigerant discharge pipe 14, a gas extension pipe 15, and a liquid extension pipe 16.

The compressor 1 is formed with a suction port 1a and a discharge port 1b. Four ports E to H are formed in the four-way valve 2. The first heat exchanger 3 is provided with two ports P1 and P2. The second heat exchanger 5 is provided with two ports P3 and P4.

The gas pipe 11 connects one port P 3 of the second heat exchanger 5 and the port E of the four-way valve 2. The liquid pipe 12 connects the other port P 4 of the second heat exchanger 5 and the pressure reducing device 4. The refrigerant suction pipe 13 connects the port F of the four-way valve 2 to the suction port 1 a of the compressor 1. The refrigerant discharge pipe 14 connects the port H of the four-way valve 2 and the discharge port 1 b of the compressor 1. The gas extension pipe 15 connects the port G of the four-way valve 2 and the port P1 of the first heat exchanger 3. The liquid extension pipe 16 connects the port P 2 of the first heat exchanger 3 and the pressure reducing device 4.

The compressor 1 compresses the refrigerant sucked from the suction port 1a, and discharges the high temperature and high pressure gas phase refrigerant from the discharge port 1b. The compressor 1 is filled with a refrigerator oil for lubricating internal parts. A part of the refrigeration oil inside the compressor 1 is discharged from the discharge port 1 b together with the refrigerant when the compressor 1 is in operation.

The four-way valve 2 is controlled by the control device 10 described later to be in either the heating operation state or the cooling operation state. In the heating operation state, the port E and the port F communicate with each other, and the port G and the port H communicate with each other. In the cooling operation state, the port E and the port H are in communication, and the port F and the port G are in communication.

The first heat exchanger 3 exchanges heat between the refrigerant and the room air. The first heat exchanger 3 operates as an evaporator in the cooling operation, and operates as a condenser in the heating operation. The first heat exchanger 3 blows room air toward the fins, for example, a heat transfer pipe for passing the refrigerant, a fin for increasing the heat transfer area between the refrigerant flowing through the heat transfer pipe and the room air, and And a blower.

The pressure reducing device 4 expands and reduces the pressure of the refrigerant passing therethrough. The pressure reducing device 4 is formed of, for example, an electronic expansion valve capable of changing the opening degree.

The second heat exchanger 5 exchanges heat between the refrigerant and the outdoor air. The second heat exchanger 5 operates as a condenser in the cooling operation, and operates as an evaporator in the heating operation. For example, the second heat exchanger 5 blows room air toward the fins and a fin for increasing a heat transfer area between the refrigerant flowing through the heat transfer tube and the room air, and a heat transfer tube through which the refrigerant passes. And a blower.

The refrigeration cycle apparatus 100 further includes a timer 50, a sensor 51, and the control device 10.

The timer 50 counts the operating time of the compressor 1. The sensor 51 detects the degree of superheat of the refrigerant between the gas extension pipe 15 and the first heat exchanger 3. The sensor 51 measures the temperature and pressure of the refrigerant, and calculates the degree of superheat from the measured temperature and pressure.

Control device 10 controls refrigerant circuit 20 to switch the operation mode of refrigeration cycle device 100. The control device 10 includes a central processing unit (CPU), a storage device, an input / output buffer, and the like (all are not shown). The CPU executes the program stored in the storage device to switch the operation mode of the refrigeration cycle apparatus 100.

When receiving the cooling operation instruction, the control device 10 controls the four-way valve 2 to the cooling operation state, and operates the refrigeration cycle apparatus 100 in the cooling operation mode. In the cooling operation mode, the refrigerant is the compressor 1, the refrigerant discharge pipe 14, the four-way valve 2, the gas pipe 11, the second heat exchanger 5, the liquid pipe 12, the pressure reducing device 4, the liquid extension pipe 16, the first heat exchanger 3, the gas extension pipe 15, the four-way valve 2, and the refrigerant suction pipe 13 circulate in this order. When the control device 10 receives the heating operation instruction, the control device 10 controls the four-way valve 2 to the heating operation state, and operates the refrigeration cycle apparatus 100 in the heating operation mode. In the heating operation mode, the refrigerant is the compressor 1, the refrigerant discharge pipe 14, the four-way valve 2, the gas extension pipe 15, the first heat exchanger 3, the liquid extension pipe 16, the pressure reducing device 4, the liquid pipe 12, the second heat exchange , The gas pipe 11, the four-way valve 2, and the refrigerant suction pipe 13 in this order. In FIG. 1, the flow direction of the refrigerant in the heating operation mode is indicated by an arrow.

As described above, the first heat exchanger 3 is installed indoors, and the compressor 1, the four-way valve 2, the pressure reducing device 4 and the second heat exchanger 5 are installed outdoors. Therefore, the gas extension pipe 15 and the liquid extension pipe 16 are longer than the gas pipe 11, the liquid pipe 12, the refrigerant suction pipe 13, and the refrigerant discharge pipe 14. Furthermore, when the first heat exchanger 3 is installed at a position higher than the outdoor unit, at least a part of the gas extension pipe 15 and the liquid extension pipe 16 is disposed along the vertical direction. Therefore, when the refrigeration cycle apparatus 100 is operating in the heating operation mode, the refrigerator oil discharged together with the refrigerant in the gas phase state from the compressor 1 can pass through the gas extension pipe 15 extending long and upward. As a result, the gas is easily retained in the gas extension pipe 15. Therefore, the controller 10 switches the operation mode of the refrigeration cycle apparatus 100 between the heating operation mode and the oil recovery operation mode in order to recover the refrigeration oil accumulated in the gas extension pipe 15 in the compressor 1.

FIG. 2 is a diagram showing the flow direction of the refrigerant in the oil recovery operation mode in the first embodiment. As shown in FIG. 2, in the oil recovery operation mode, the control device 10 controls the four-way valve 2 to the cooling operation state. Therefore, the refrigerant circulates through the refrigerant circuit 20 as in the cooling operation mode. That is, the refrigerant flows in the opposite direction to the heating operation mode. Thereby, when the gas extension pipe 15 is disposed upward toward the first heat exchanger 3, the flow direction of the refrigerant in the gas extension pipe 15 is oil recovery while it is upward in the heating operation mode. In the operation mode, it is downward. As a result, refrigeration oil accumulated in the gas extension pipe 15 can be easily returned to the compressor 1.

Furthermore, the control device 10 controls the refrigerant circuit 20 so that the degree of superheat output from the sensor 51 becomes 0 K or less. For example, the control device 10 controls the degree of pressure reduction of the pressure reducing device 4 or controls the heat exchange capacity of the first heat exchanger 3. The degree of pressure reduction of the pressure reducing device 4 is controlled by the degree of opening of the pressure reducing device 4 which is an expansion valve. Thus, the gas-liquid two-phase refrigerant flows through the gas extension pipe 15. As a result, the refrigeration oil accumulated in the gas extension pipe 15 dissolves in the refrigerant in the gas-liquid two-phase state and easily moves, and is easily recovered by the compressor 1.

The control device 10 switches the operation mode every specified time based on the integrated value of the operation time counted by the timer 50. Specifically, when the heating operation mode continues for the first specified time, the control device 10 switches the operation mode of the refrigeration cycle device to the oil recovery operation mode. The control device 10 switches the operation mode of the refrigeration cycle apparatus to the heating operation mode when the oil recovery operation mode continues for the second specified time.

(Flow of processing of control device)
FIG. 3 is a flowchart showing the flow of processing of the control device 10 according to the first embodiment. FIG. 3 shows the process when the heating operation instruction is received. First, in step S1, the control device 10 receives a heating operation instruction. In step S2, the control device 10 controls the four-way valve 2 to the heating operation state, and starts the operation in the heating operation mode. In step S3, the control device 10 controls the timer 50 to start counting operation time.

Next, in step S4, the control device 10 determines whether or not the integrated value A of the operating time is less than the first specified time B. If the integrated value A of the operating time is less than the first prescribed time B (YES in step S4), the process returns to step S4. If the integrated value A of the operating time is equal to or greater than the first specified time B (NO in step S4), the control device 10 switches the operating mode of the refrigeration cycle apparatus 100 to the oil recovery operating mode in step S5. That is, the control device 10 switches the four-way valve 2 to the cooling operation state. Further, the control device 10 resets the integrated value A of the operation time to 0 in step S6, and acquires the degree of superheat indicating the refrigerant state between the gas extension pipe 15 and the first heat exchanger 3 from the sensor 51 in step S7. Do. In step S8, the control device 10 determines whether the degree of superheat acquired from the sensor 51 is 0 K or less. If the degree of superheat is greater than 0 K (NO in step S8), control device 10 controls refrigerant circuit 20 so that the degree of superheat decreases in step S9. For example, the controller 10 increases the opening degree of the pressure reducing device 4. Alternatively, the control device 10 weakens the blowing amount of the blower of the first heat exchanger 3.

After step S9, control device 10 determines whether integrated value A of the operating time is less than second prescribed time C or not in step S10. Here, the integrated value A of the operating time indicates the elapsed time from step S6. If the degree of superheat is 0 K or less (YES in step S8), the process also proceeds to step S10. If the integrated value A of the operating time is less than the second specified time C (YES in step S10), the process returns to step S7. That is, control is performed so that the refrigerant between the gas extension pipe 15 and the first heat exchanger 3 is in a gas-liquid two-phase state until the second specified time C elapses after the oil recovery operation mode is started. Be done. The refrigerant in the gas-liquid two-phase state continues to flow through the gas extension pipe 15 in the opposite direction to the heating operation mode. Thus, the refrigeration oil accumulated in the gas extension pipe 15 in the heating operation mode moves with the refrigerant in the gas-liquid two-phase state in the oil recovery operation mode, and is recovered by the compressor 1.

When the integrated value A of the operating time becomes equal to or greater than the second prescribed time C (NO in step S10), the control device 10 returns the operating mode of the refrigeration cycle apparatus 100 to the heating operation mode in step S11. Reset integrated value A to 0. After step S12, the process returns to step S4.

(advantage)
As described above, the refrigeration cycle apparatus 100 according to the first embodiment includes the refrigerant circuit 20 and the control device 10. The refrigerant circuit 20 is a circuit in which the compressor 1, the first heat exchanger 3, the pressure reducing device 4 and the second heat exchanger 5 are connected by a refrigerant pipe. When receiving the heating operation instruction, the control device 10 switches the operation mode of the refrigeration cycle apparatus 100 between the heating operation mode (first operation mode) and the oil recovery operation mode (second operation mode). The refrigerant pipe includes a gas extension pipe (first pipe) 15 connected to the port (first port) P1 of the first heat exchanger 3. The heating operation mode is a mode in which the refrigerant is circulated in the refrigerant circuit 20 so that the refrigerant in the gas phase flows into the gas extension pipe 15. The oil recovery operation mode is a mode in which the refrigerant is circulated in the refrigerant circuit 20 so that the gas-liquid two-phase refrigerant flows into the gas extension pipe 15. The gas extension pipe 15 constitutes a flow path between the compressor 1 and the first heat exchanger 3 in the heating operation mode. The flow direction of the refrigerant in the gas extension pipe 15 in the oil recovery operation mode is opposite to the flow direction of the refrigerant in the gas extension pipe 15 in the heating operation mode.

According to said structure, the gas extension piping 15 comprises the flow path between the compressor 1 and the 1st heat exchanger 3 in heating operation mode. The refrigeration oil discharged from the compressor 1 flows in the gas extension pipe 15 together with the refrigerant in the gas phase. However, refrigerator oil is hard to move because it has high viscosity. In the case where the gas extension pipe 15 is disposed in the vertical direction and the flow of the refrigerant is upward, the refrigerator oil becomes more difficult to move. As a result, refrigeration oil stagnates in the gas extension pipe 15.

The controller 10 switches the operation mode of the refrigeration cycle apparatus 100 between the heating operation mode and the oil recovery operation mode in order to recover the refrigeration oil accumulated in the gas extension pipe 15 in the compressor 1. In the oil recovery operation mode, the gas-liquid two-phase refrigerant flows into the gas extension pipe 15. Refrigerant oil dissolves in the gas-liquid two-phase refrigerant and becomes easy to move. Therefore, it becomes easy to collect refrigeration oil which has been stagnated in the compressor 1. Furthermore, the flow direction of the refrigerant in the gas extension pipe 15 in the oil recovery operation mode is opposite to the flow direction of the refrigerant in the gas extension pipe 15 in the heating operation mode. Therefore, even if the gas extension pipe 15 is disposed vertically upward toward the first heat exchanger 3, refrigeration oil can be easily recovered to the compressor 1.

As described above, the refrigeration oil can be recovered to the compressor 1 without raising the operating frequency of the compressor 1 in a state where the refrigeration oil is small. That is, while suppressing generation | occurrence | production of a failure of the compressor 1, refrigeration oil can be collect | recovered to a compressor.

The refrigeration cycle apparatus 100 further includes a sensor 51 for detecting the state of the refrigerant between the gas extension pipe 15 and the first heat exchanger 3. The refrigerant circuit 20 includes a four-way valve 2 for switching the flow direction of the refrigerant in the refrigerant circuit 20. The control device 10 controls the four-way valve 2 to switch between the heating operation mode and the oil recovery operation mode. In the heating operation mode, the refrigerant circulates in the order of the compressor 1, the four-way valve 2, the gas extension pipe 15, the first heat exchanger 3, the pressure reducing device 4, the second heat exchanger 5, and the four-way valve 2 (gas pipe 11 The description of the liquid pipe 12, the refrigerant suction pipe 13 and the refrigerant discharge pipe 14 is omitted, and the description will be similarly omitted below. In the oil recovery operation mode, the refrigerant circulates in the order of the compressor 1, the four-way valve 2, the second heat exchanger 5, the pressure reducing device 4, the first heat exchanger 3, the gas extension pipe 15 and the four-way valve 2. The control device 10 controls the refrigerant circuit 20 so that the state detected by the sensor 51 indicates a gas-liquid two-phase state in the oil recovery operation mode. For example, the control device 10 may control the degree of pressure reduction of the pressure reducing device 4 or the heat exchange capacity of the first heat exchanger 3.

Thereby, the control device 10 controls the four-way valve 2 to reverse the flow direction of the refrigerant in the gas extension pipe 15 in the oil recovery operation mode to the flow direction of the refrigerant in the gas extension pipe 15 in the heating operation mode. Can be Furthermore, based on the detection result of the sensor 51, the control device 10 can reliably cause the gas-liquid two-phase refrigerant to flow through the gas extension pipe 15.

The control device 10 switches the operation mode of the refrigeration cycle apparatus 100 to the oil recovery operation mode when the heating operation mode continues for the first prescribed time B, and performs refrigeration when the oil recovery operation mode continues for the second prescribed time C. The operation mode of the cycle apparatus 100 is switched to the heating operation mode.

As a result, the operation mode is switched every specified time, so that the refrigeration oil accumulated in the gas extension pipe 15 is periodically collected by the compressor 1.

Second Embodiment
(Configuration of refrigeration cycle device)
FIG. 4 is a schematic configuration diagram of a refrigeration cycle apparatus according to a second embodiment. As shown in FIG. 4, a refrigeration cycle apparatus 100 a according to the second embodiment includes a refrigerant circuit 20 a instead of the refrigerant circuit 20 as compared to the refrigeration cycle apparatus 100 according to the first embodiment, and a control device 10. In that the controller 10a is provided instead of the controller 10a. The refrigerant circuit 20a is different from the refrigerant circuit 20 shown in FIG. 1 in that the refrigerant circuit 20a includes the flow path switching circuit 8.

The flow path switching circuit 8 includes four gate valves 81 to 84. The gate valve 81 is disposed between the port G of the four-way valve 2 and the gas extension pipe 15 to open and close the flow path between the two. The gate valve 82 is disposed between the port G of the four-way valve 2 and the liquid extension pipe 16 to open and close the flow path between the two. The gate valve 83 is disposed between the pressure reducing device 4 and the gas extension pipe 15 to open and close the flow path between them. The gate valve 84 is disposed between the pressure reducing device 4 and the liquid extension pipe 16 to open and close the flow path between them.

The control device 10a controls the four-way valve 2 and the flow path switching circuit 8 to switch the operation mode of the refrigeration cycle apparatus 100a to any of the heating operation mode, the cooling operation mode, and the oil recovery operation mode. Hereinafter, the heating operation mode and the cooling operation mode are collectively referred to as a normal operation mode.

As in the control device 10 of the first embodiment, the control device 10a controls the four-way valve 2 to switch from the cooling operation mode to the heating operation mode or from the heating operation mode to the cooling operation mode.

Furthermore, the control device 10a controls the flow path switching circuit 8 to switch the operation mode of the refrigeration cycle apparatus 100a between the normal operation mode (the cooling operation mode or the heating operation mode) and the oil recovery operation mode. The control device 10a controls the

gate valves

81 and 84 in the open state and the

gate valves

82 and 83 in the closed state in the normal operation mode. By controlling the

gate valves

81 and 84 in the open state and the

gate valves

82 and 83 in the closed state, the compressor 1 and the gas extension pipe 15 are connected, and the pressure reducing device 4 and the liquid extension pipe 16 are connected. Connected (first connection state). In the oil recovery operation mode, the control device 10a controls the

gate valves

81 and 84 in the closed state and the

gate valves

82 and 83 in the open state. By controlling the

gate valves

81 and 84 in the closed state and the

gate valves

82 and 83 in the open state, the compressor 1 and the liquid extension pipe 16 are connected, and the pressure reducing device 4 and the gas extension pipe 15 are connected. Connected (second connection state).

In FIG. 4, the flow of the refrigerant in the heating operation mode is indicated by an arrow. As shown in FIG. 4, in the heating operation mode, the refrigerant is the compressor 1, the four-way valve 2, the gate valve 81, the gas extension pipe 15, the first heat exchanger 3, the liquid extension pipe 16, the gate valve 84, the pressure reduction The apparatus 4, the second heat exchanger 5 and the four-way valve 2 circulate in this order.

FIG. 5 is a diagram showing the flow of the refrigerant when the heating operation mode is switched to the oil recovery operation mode. As shown in FIG. 5, in the oil recovery operation mode during heating operation, the refrigerant is the compressor 1, the four-way valve 2, the gate valve 82, the liquid extension pipe 16, the first heat exchanger 3, the gas extension pipe 15, The gate valve 83, the pressure reducing device 4, the second heat exchanger 5, and the four-way valve 2 circulate in this order.

As shown in FIGS. 4 and 5, the flow direction of the refrigerant in the gas extension pipe 15 in the oil recovery operation mode is opposite to the flow direction of the refrigerant in the gas extension pipe 15 in the heating operation mode. Thereby, when the gas extension pipe 15 is disposed upward toward the first heat exchanger 3, the flow direction of the refrigerant in the gas extension pipe 15 is oil recovery while it is upward in the heating operation mode. In the operation mode, it is downward. As a result, in the oil recovery operation mode, refrigeration oil accumulated in the gas extension pipe 15 in the heating operation mode can be easily returned to the compressor 1.

Furthermore, in the oil recovery operation mode, the refrigerant in the liquid phase or gas-liquid two-phase state condensed in the first heat exchanger 3 flows through the gas extension pipe 15. As a result, the refrigeration oil accumulated in the gas extension pipe 15 dissolves in the liquid phase or the gas-liquid two-phase refrigerant and moves easily, and the pressure reducing device 4, the second heat exchanger 5 and the four-way valve 2 It passes and is easily recovered to the compressor 1.

FIG. 6 is a diagram showing the flow of the refrigerant in the cooling operation mode in the second embodiment. As shown in FIG. 6, in the cooling operation mode, the refrigerant is the compressor 1, the four-way valve 2, the second heat exchanger 5, the pressure reducing device 4, the gate valve 84, the liquid extension piping 16, the first heat exchanger 3. , The gas extension pipe 15, the gate valve 81, and the four-way valve 2 in this order. In the cooling operation mode, the refrigerant in the liquid phase or the gas-liquid two-phase state flowing in the liquid extension pipe 16 is evaporated by the first heat exchanger 3, and the refrigerant in the gas phase flows in the gas extension pipe 15. Refrigerating machine oil which has been dissolved in the liquid phase or gas-liquid two phase refrigerant in the liquid extension pipe 16 is separated from the refrigerant in the first heat exchanger 3 and may stay in the gas extension pipe 15. Therefore, the operation mode of the refrigeration cycle apparatus 100a is switched between the cooling operation mode and the oil recovery operation mode.

FIG. 7 is a diagram showing the flow of the refrigerant when the cooling operation mode is switched to the oil recovery operation mode. As shown in FIG. 7, in the oil recovery operation mode during the cooling operation, the refrigerant is received by the compressor 1, the four-way valve 2, the second heat exchanger 5, the pressure reducing device 4, the gate valve 83, the

gas extension pipe

15, 1 Heat exchanger 3, liquid extension pipe 16, gate valve 82 and four-way valve 2 circulate in this order.

As shown in FIGS. 6 and 7, the flow direction of the refrigerant in the gas extension pipe 15 in the oil recovery operation mode is opposite to the flow direction of the refrigerant in the gas extension pipe 15 in the cooling operation mode. Furthermore, in the oil recovery operation mode, the refrigerant in the liquid phase or in the gas-liquid two-phase state flows through the gas extension pipe 15. Thus, the refrigeration oil accumulated in the gas extension pipe 15 in the cooling operation mode can be recovered to the compressor 1.

(Flow of processing of control device)
FIG. 8 is a flowchart showing the process flow of the control device 10a according to the second embodiment. First, in step S21, the control device 10a receives an instruction for normal operation (cooling operation or heating operation). In step S22, the control device 10a controls the four-way valve 2 according to the instruction and starts operation in the normal operation mode. That is, when the control device 10a receives the cooling operation instruction, it controls the four-way valve 2 to the cooling operation state to start the operation in the cooling operation mode, and receives the heating operation instruction. The heating operation mode is controlled to start the operation in the heating operation mode. At this time, the control device 10a controls the

gate valves

81 and 84 in the open state and the

gate valves

82 and 83 in the closed state. In step S23, the control device 10a controls the timer 50 to start counting operation time.

Next, in step S24, the control device 10a determines whether the integrated value A of the operating time is less than the first specified time B. If the integrated value A of the operating time is less than the first prescribed time B (YES in step S24), the process returns to step S24. When the integrated value A of the operating time becomes equal to or greater than the first prescribed time B (NO in step S24), the controller 10a switches the operating mode of the refrigeration cycle apparatus 100a to the oil recovery operating mode in step S25. That is, the control device 10a controls the

gate valves

81 and 84 in the closed state and the

gate valves

82 and 83 in the open state. Further, in step S26, the control device 10a resets the integrated value A of the operating time to zero.

After step S26, the control device 10a determines whether or not the integrated value A of the operating time is less than the second specified time C in step S27. Here, the integrated value A of the operation time indicates the elapsed time from step S26, that is, the continuation time of the oil recovery operation mode. If the integrated value A of the operating time is less than the second specified time C (YES in step S27), the process returns to step S26. That is, the flow direction of the refrigerant in the gas extension pipe 15 is opposite to the flow direction in the normal operation mode until the second specified time C elapses after the oil recovery operation mode is started. Furthermore, a refrigerant in a liquid phase or in a gas-liquid two-phase state flows through the gas extension pipe 15. As a result, the refrigeration oil accumulated in the gas extension pipe 15 in the normal operation mode is recovered by the compressor 1 in the oil recovery operation mode.

When integrated value A of the operating time becomes equal to or greater than second prescribed time C (YES in step S27), control device 10a returns the operating mode of refrigeration cycle apparatus 100a to the normal operating mode in step S28, and in step S29 Reset integrated value A to 0. After step S29, the process returns to step S24.

(advantage)
The refrigerant circuit 20a of the refrigeration cycle apparatus 100a according to the second embodiment has the flow path switching circuit 8 configured to switch the connection state of the compressor 1, the pressure reducing device 4, the gas extension pipe 15, and the liquid extension pipe 16. Including. The liquid extension pipe 16 is a pipe connected to the port (second port) P2 of the first heat exchanger 3. The flow path switching circuit 8 switches the connection state between the compressor 1, the pressure reducing device 4, the gas extension pipe 15, and the liquid extension pipe 16 to either the first connection state or the second connection state. The first connection state is a state in which the compressor 1 and the gas extension pipe 15 are connected via the four-way valve 2 and the pressure reducing device 4 and the liquid extension pipe 16 are connected. The second connection state is a state in which the compressor 1 and the liquid extension pipe 16 are connected via the four-way valve 2 and the pressure reducing device 4 and the gas extension pipe 15 are connected. The control device 10a switches the operation mode of the refrigeration cycle apparatus 100a to the normal operation mode by switching the flow path switching circuit 8 to the first connection state. The control device 10a switches the operation mode of the refrigeration cycle apparatus 100a to the oil recovery operation mode by switching the flow path switching circuit 8 to the second connection state.

When the flow path switching circuit 8 is in the first connection state when the four-way valve 2 is in the heating operation state, the refrigerant is the compressor 1, the four-way valve 2, the gate valve 81, the gas extension pipe 15, the first heat exchange , The liquid extension pipe 16, the gate valve 84, the pressure reducing device 4, the second heat exchanger 5, and the four-way valve 2 in this order (heating operation mode). On the other hand, when the flow path switching circuit 8 is in the second connection state, the refrigerant is the compressor 1, the four-way valve 2, the gate valve 82, the liquid extension pipe 16, the first heat exchanger 3, the gas extension pipe 15, the gate valve 83, the pressure reducing device 4, the second heat exchanger 5, and the four-way valve 2 circulate in this order (oil recovery operation mode).

When the flow path switching circuit 8 is in the first connection state when the four-way valve 2 is in the cooling operation state, the refrigerant is the compressor 1, the four-way valve 2, the second heat exchanger 5, the pressure reducing device 4, the gate valve 84, the liquid extension piping 16, the first heat exchanger 3, the gas extension piping 15, the gate valve 81, and the four-way valve 2 are circulated in this order (cooling operation mode). On the other hand, when the flow path switching circuit 8 is in the second connection state, the refrigerant is the compressor 1, the four-way valve 2, the second heat exchanger 5, the pressure reducing device 4, the gate valve 83, the gas extension pipe 15, the first heat The exchanger 3, the liquid extension pipe 16, the gate valve 82, and the four-way valve 2 circulate in this order (oil recovery operation mode).

As described above, in order to recover the refrigeration oil accumulated in the gas extension pipe 15 to the compressor 1, the control device 10a sets the operation mode of the refrigeration cycle apparatus 100 to the normal operation mode (heating operation mode or cooling operation mode) Switch between the recovery operation mode. In the oil recovery operation mode, the refrigerant in the liquid phase or in the gas-liquid two-phase state flows to the gas extension pipe 15. Refrigerant oil dissolves in a liquid phase or a gas-liquid two-phase refrigerant and becomes easy to move. Furthermore, the flow direction of the refrigerant in the gas extension pipe 15 in the oil recovery operation mode is opposite to the flow direction of the refrigerant in the gas extension pipe 15 in the normal operation mode. Therefore, even when the gas extension pipe 15 is disposed in the vertical direction, the refrigeration oil can be easily recovered to the compressor 1. As described above, the refrigeration oil can be recovered to the compressor 1 without raising the operating frequency of the compressor 1 in a state where the refrigeration oil is small. That is, refrigeration oil can be recovered to the compressor without applying a large load to the compressor.

Furthermore, the order in which the refrigerant flows through the compressor, the first heat exchanger, the pressure reducing device and the second heat exchanger is the same in the normal operation mode and the oil recovery operation mode. Therefore, the first heat exchanger operating as the evaporator in the normal operation mode can operate as the evaporator even in the oil recovery operation mode. Similarly, the first heat exchanger operating as a condenser in the normal operation mode can operate as a condenser also in the oil recovery operation mode. Thereby, the fall of comfort in a room can be controlled in oil recovery operation mode. Further, as shown in FIG. 13, in the oil recovery operation of the prior art, the room temperature temporarily deviates from the target value to reduce the comfortability in order to increase the operation frequency of the compressor. However, in the refrigeration cycle apparatus 100a according to the second embodiment, since the operating frequency of the compressor 1 is not changed when switching from the normal operation mode to the oil recovery operation mode, it is possible to suppress the decrease in comfort.

Modification 1
When a pipe with an inner diameter di is arranged along the vertical direction and the refrigerant in the gas phase with density gg and the refrigeration oil with density ll flow upward into the pipe, the flow velocity Ug of the refrigerant in gas phase is the following equation When it is equal to or higher than the oil rising limit speed Ug * shown in (1), the refrigerator oil rises along the piping. g is gravity acceleration.

FIG. 9 is a view showing the state of the refrigerating machine oil in the pipe when the flow velocity Ug of the refrigerant in the gas phase is equal to or higher than the oil rising limit velocity Ug *. As shown in FIG. 9, since the flow velocity Ug of the refrigerant in the gas phase is equal to or higher than the oil rising limit velocity Ug *, the refrigerator oil 30 rises along the wall of the pipe.

In the above first and second embodiments, it is preferable that the inner diameter di of at least a part of the gas extension pipe 15 satisfy the following equation (2). In the following equation (2), Uga represents the flow rate of the refrigerant in the gas phase when the compressor 1 is operated at the minimum operating frequency. The right side of Formula (2) shows oil rising limit speed Ug *.

FIG. 10 is a view showing the state of the refrigerator oil in the gas extension pipe according to the first modification. In FIG. 10, the inside of the gas extension pipe 15 is frozen when the inner diameter di of the portion 15a of the gas extension pipe 15 satisfies the above equation (2) and the inner diameter of the remaining portion 15b does not satisfy the above equation (2). The machine oil is shown. When the indoor temperature approaches the target temperature and the refrigeration cycle apparatus 100 is intermittently operated, the compressor 1 is operated at the minimum operating frequency. When the compressor 1 is operated at the minimum operating frequency, the flow velocity Uga of the refrigerant in the portion 15a is less than the oil rising limit velocity Ug *. Therefore, as shown in FIG. 10, the refrigerator oil 30 tends to stay in the portion 15a.

On the other hand, the flow velocity Ugb of the refrigerant in the portion 15b is equal to or higher than the oil rising limit velocity Ug *. Therefore, the refrigerator oil 30 hardly stagnates in the portion 15b. Furthermore, since most of the refrigeration oil 30 discharged from the compressor 1 stays in the portion 15a, the amount of refrigeration oil 30 flowing into the downstream portion 15b of the portion 15a is small.

As described above, when the portion 15 a of the gas extension pipe 15 is vertically disposed from the outdoor unit toward the first heat exchanger 3, most of the refrigerator oil 30 discharged from the compressor 1 is the gas extension pipe 15. Stay in part 15a of As a result, in the portion of the refrigerant circuit 20 other than the gas extension pipe 15, it is possible to suppress the pressure loss and the heat transfer performance deterioration due to the stagnation of the refrigeration oil 30. As a result, the air conditioning performance of the

refrigeration cycle apparatus

100, 100a can be improved.

Furthermore, the refrigeration oil 30 retained in the portion 15 a of the gas extension pipe 15 is dissolved in the liquid phase or gas-liquid two-phase refrigerant in the oil recovery operation mode, and is easily recovered by the compressor 1. Therefore, the reliability of the compressor 1 can be improved.

Modification 2
In the first embodiment described above, control device 10 may set the minimum operating frequency of compressor 1 as follows. The controller 10 is configured such that the flow velocity Ugc of the refrigerant in the gas extension pipe 15 when operating the compressor 1 at the minimum operating frequency is less than the oil rising limit velocity Ug * represented by the above equation (1). , Set the minimum operating frequency of the compressor 1.

FIG. 11 is a view showing the state of the refrigerator oil in the gas extension pipe according to the second modification. When operating the compressor 1 at the minimum operating frequency, the flow velocity Ugc of the refrigerant is less than the oil rising limit velocity Ug *. Therefore, as shown in FIG. 11, when at least a part of the gas extension pipe 15 is vertically disposed from the outdoor unit toward the first heat exchanger 3, the refrigerator oil 30 is formed on the wall surface of the gas extension pipe 15. Stay. By retaining most of the refrigeration oil 30 discharged from the compressor 1 in the gas extension piping 15, pressure loss and heat transfer performance deterioration due to the residence of the refrigeration oil 30 in portions other than the gas extension piping 15 in the refrigerant circuit 20 It can be suppressed. As a result, the air conditioning performance of the refrigeration cycle apparatus 100 can be improved.

Furthermore, the refrigeration oil 30 retained in the gas extension pipe 15 is dissolved in the liquid phase or gas-liquid two-phase refrigerant in the oil recovery operation mode, and is easily recovered by the compressor 1. Therefore, the reliability of the compressor 1 can be improved.

Similarly in the second embodiment, control device 10a is configured such that the flow velocity Ugc of the refrigerant in gas extension piping 15 when compressor 1 is operated at the minimum operating frequency is less than the oil rising limit velocity Ug *. The minimum operating frequency of the compressor 1 may be set.

Modification 3
In the second embodiment described above, the control device 10a controls the flow path switching circuit 8 to control the flow direction of the refrigerant and the flow of air in the first heat exchanger 3 in any of the heating operation mode and the cooling operation mode. The direction may be opposed. Thereby, the heat exchange capacity of the first heat exchanger 3 can be enhanced.

FIG. 12 is a diagram showing the flow of the refrigerant before and after switching from the heating operation to the cooling operation. Here, the flow direction AD of air by the blower 3c of the first heat exchanger 3 is a direction from the port P2 of the first heat exchanger 3 toward the port P1.

As shown in FIG. 12, in the heating operation mode, the control device 10 a places the four-way valve 2 in the heating operation state, and the flow path switching circuit 8 in the first connection state (

separator valves

81 and 84 open; , 83 in the closed state). Thereby, the refrigerant is the compressor 1, the four-way valve 2, the gate valve 81, the gas extension pipe 15, the first heat exchanger 3, the liquid extension pipe 16, the gate valve 84, the pressure reducing device 4, the second heat exchanger 5 and It circulates in order of the four-way valve 2. Therefore, in the first heat exchanger 3, the flow direction of the refrigerant (the direction from the port P1 toward the port P2) faces the flow direction AD of the air.

When a switching instruction from the heating operation to the cooling operation is received, the control device 10a places the four-way valve 2 in the cooling operation state and the flow path switching circuit 8 in the second connection state (the

partition valves

81 and 84 are closed, the

gate valve

82 , 83 in the open state). Thus, the refrigerant is compressed into the compressor 1, the four-way valve 2, the second heat exchanger 5, the pressure reducing device 4, the gate valve 83, the gas extension pipe 15, the first heat exchanger 3, the liquid extension pipe 16, and the gate valve 82. And circulate in the order of the four-way valve 2. Therefore, also in the cooling operation mode, the flow direction of the refrigerant (the direction from the port P1 to the port P2) in the first heat exchanger 3 opposes the flow direction AD of the air. Thereby, the heat exchange capacity of the first heat exchanger 3 can be improved in both the heating operation and the cooling operation.

When the air flow direction AD by the blower 3c of the first heat exchanger 3 is a direction from the port P1 to the port P2 of the first heat exchanger 3, the gate valves 81 to 84 are controlled reversely to the above. Be done. That is, in the cooling operation mode, the control device 10a sets the four-way valve 2 in the cooling operation state, the flow path switching circuit 8 in the first connection state (the

partition valves

81 and 84 open, and the

partition valves

82 and 83 close) Control). Thereby, the refrigerant is the compressor 1, the four-way valve 2, the second heat exchanger 5, the pressure reducing device 4, the gate valve 84, the liquid extension pipe 16, the first heat exchanger 3, the gas extension pipe 15, the gate valve 81 and It circulates in order of the four-way valve 2. When receiving a switching instruction from the cooling operation to the heating operation, the control device 10a places the four-way valve 2 in the heating operation state and the flow path switching circuit 8 in the second connection state (the

gate valve

81, 84 is closed,

gate valve

82 , 83 in the open state). As a result, the refrigerant is compressed into the compressor 1, the four-way valve, the gate valve 82, the liquid extension pipe 16, the first heat exchanger 3, the gas extension pipe 15, the gate valve 83, the pressure reducing device 4, the second heat exchanger 5, and It circulates in order of the valve 2. As described above, in both the heating operation mode and the cooling operation mode, the flow direction of the refrigerant in the first heat exchanger 3 and the flow direction of the air face each other. As a result, the heat exchange capacity of the first heat exchanger 3 can be improved in both the heating operation and the cooling operation.

Modification 4
In the first embodiment described above, the control device 10 switches between the heating operation mode and the oil recovery operation mode based on the operation time of the compressor 1. On the other hand, the refrigeration cycle apparatus 100 includes a measuring device for measuring the amount of refrigeration oil in the compressor 1, and the control device 10 performs the heating operation mode and the oil recovery operation based on the amount of refrigeration oil measured by the measuring device. The mode may be switched. Specifically, the control device 10 switches from the heating operation mode to the oil recovery operation mode when the amount of refrigeration oil becomes less than the first threshold. Furthermore, the control device 10 switches from the oil recovery operation mode to the heating operation mode after operating the oil recovery operation mode for a specified time or when the amount of refrigeration oil exceeds the second threshold (> first threshold). return.

Similarly in the second embodiment, the control device 10a may switch between the normal operation mode and the oil recovery operation mode based on the amount of refrigeration oil in the compressor 1.

Modification 5
In the second embodiment, the flow path switching circuit 8 is configured by four gate valves 81 to 84. However, if the flow path switching circuit 8 can switch the connection state between the compressor 1, the pressure reducing device 4, the gas extension pipe 15, and the liquid extension pipe 16 to either the first connection state or the second connection state, It may be composed of another member. For example, the flow path switching circuit 8 may be configured by a four-way valve.

Modification 6
In the first and second embodiments, an accumulator may be installed in the refrigerant suction pipe 13 in order to prevent the refrigerant in the liquid phase from being drawn into the compressor 1. Furthermore, an oil recovery unit for recovering refrigeration oil may be installed in the gas extension pipe 15. In this case, refrigeration oil is recovered by the oil recovery unit in the normal operation mode, and refrigeration oil is returned from the oil recovery unit to the compressor in the oil recovery operation mode.

It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of claims.

Reference Signs List 1 compressor, 1a suction port, 1b discharge port, 2 four-way valve, 3 first heat exchanger, 3c fan, 4 pressure reducing device, 5 second heat exchanger, 8 flow path switching circuit, 10, 10a control device, 11 Gas pipes, 12 liquid pipes, 13 refrigerant suction pipes, 14 refrigerant discharge pipes, 15 gas extension pipes, 15a, 15b parts, 16 liquid extension pipes, 20, 20a refrigerant circuits, 50 timers, 51 sensors, 81 to 84 gate valves, 100, 100a Refrigeration cycle equipment, E to H, P1 to P4 ports.

Claims

A refrigeration cycle apparatus comprising a refrigerant circuit in which a compressor, a first heat exchanger, a pressure reducing device, and a second heat exchanger are connected by a refrigerant pipe,
It has a control device that switches the operation mode of the refrigeration cycle apparatus between a first operation mode and a second operation mode.
The refrigerant pipe includes a first pipe connected to a first port of the first heat exchanger,
The first operation mode is a mode in which the refrigerant is circulated in the refrigerant circuit such that a refrigerant in a gas phase flows into the first pipe,
The second operation mode is a mode in which the refrigerant is circulated in the refrigerant circuit such that the refrigerant in a liquid phase state or a gas-liquid two-phase state flows to the first pipe,
The first pipe constitutes a flow path between the compressor and the first heat exchanger in the first operation mode,
The refrigeration cycle apparatus, wherein the flow direction of the refrigerant in the first pipe in the second operation mode is opposite to the flow direction of the refrigerant in the first pipe in the first operation mode.
It further comprises a sensor for detecting the state of the refrigerant between the first pipe and the first heat exchanger,
The refrigerant circuit includes a four-way valve for switching the flow direction of the refrigerant in the refrigerant circuit,
The control device switches between the first operation mode and the second operation mode by switching the four-way valve.
In the first operation mode, the refrigerant circulates in the order of the compressor, the first pipe, the first heat exchanger, the pressure reducing device, and the second heat exchanger,
In the second operation mode, the refrigerant circulates in the order of the compressor, the second heat exchanger, the pressure reducing device, the first heat exchanger, and the first pipe,
The refrigeration cycle apparatus according to claim 1, wherein the control device controls the refrigerant circuit such that a state detected by the sensor indicates a gas-liquid two-phase state in the second operation mode.
The refrigerant pipe further includes a second pipe connected to a second port of the first heat exchanger,
The refrigerant circuit further includes a flow path switching circuit configured to switch a connection state of the compressor, the pressure reducing device, the first pipe, and the second pipe,
The flow path switching circuit is configured such that the connection state is a first connection state in which the compressor and the first pipe are connected and the pressure reducing device and the second pipe are connected; Switching to any one of a second connection state in which the second pipe is connected and the pressure reducing device and the first pipe are connected;
The control device switches the operation mode of the refrigeration cycle apparatus to the first operation mode by switching the flow path switching circuit to the first connection state, and switches the flow path switching circuit to the second connection state. The refrigeration cycle apparatus according to claim 1, wherein the operation mode of the refrigeration cycle apparatus is switched to the second operation mode according to.
The refrigerant circuit further includes a four-way valve for switching the flow direction of the refrigerant in the refrigerant circuit,
The refrigeration cycle apparatus according to claim 3, wherein when the control device switches the cooling operation and the heating operation by controlling the four-way valve, the control device controls the flow path switching circuit to switch the connection state.
The control device switches the operation mode of the refrigeration cycle apparatus to the second operation mode when the first operation mode continues for the first specified time, and the control device continues the second operation time for the second specified time. The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein an operation mode of the refrigeration cycle apparatus is switched to the first operation mode.
The internal diameter di of at least a portion of the first pipe g is the gravitational acceleration, the density of the refrigerant in the gas phase in the first pipe in the first operation mode is ρg, and the first pipe in the first operation mode When the density of the refrigerant oil in the interior is ρl, and the flow velocity of the refrigerant in the at least one portion when the compressor is operated at the minimum operating frequency is Uga,

The refrigeration cycle apparatus according to any one of claims 1 to 5, wherein
The control device sets the inner diameter of the first pipe to di, the gravitational acceleration g, the density of the refrigerant in the gas phase in the first pipe in the first operation mode モード g, and the first in the first operation mode The flow velocity of the refrigerant in the first pipe when the compressor is operated at the minimum operating frequency when the density of the refrigeration oil in the 1 pipe is ρl is

The refrigeration cycle apparatus according to any one of claims 1 to 5, wherein the minimum operating frequency of the compressor is set to be smaller than Ug * indicated by.